activity_main.xml

<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <View
        android:id="@+id/stopwatch_background"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:background="@color/red"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintDimensionRatio="16:9"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0" />

    <ImageButton
        android:id="@+id/start_or_pause"
        android:layout_width="@dimen/button_size"
        android:layout_height="@dimen/button_size"
        android:layout_margin="@dimen/spacing_medium"
        android:background="?attr/selectableItemBackgroundBorderless"
        android:src="@drawable/ic_play_arrow_24dp"
        app:layout_constraintBottom_toBottomOf="@id/stopwatch_background"
        app:layout_constraintEnd_toEndOf="@id/stopwatch_background"
        app:layout_constraintTop_toTopOf="@id/stopwatch_background"
        app:tint="@android:color/white" />

    <TextView
        android:id="@+id/time"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_margin="@dimen/spacing_medium"
        android:autoSizeTextType="uniform"
        android:gravity="center"
        android:maxLines="1"
        android:textColor="@android:color/white"
        app:layout_constraintBottom_toBottomOf="@id/stopwatch_background"
        app:layout_constraintEnd_toStartOf="@id/start_or_pause"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@id/stopwatch_background"
        tools:text="00:00:00:00" />

</androidx.constraintlayout.widget.ConstraintLayout>